Discolouration is something that will appear if you strain your TV. I partially agree that because video games use a broad spectrum of colour, it might stress out one of the three colour bands (red, green, blue) that make up the images. But it's no more worse than running a DVD player on the TV. This problem was more pronounced with CRT TVs because the phosphor can wear out with prolonged use.

So why have some people seen this discolouration? It's due to wear and tear. There's no mystery to it. After all, kids tend to play games much, much longer than a typical TV watching session. During my younger days, I'd play Megadrive from 8.30am to 5pm on pretty much every weekend. Can you guess how long it was before the TV died?